For a number of years, optical character readers have been used at post offices to automatically read addresses containing city, state and zip code information. This address information is utilized to automatically sort incoming mail for delivery by mail carriers. However, since the position of the address on the envelope, as well as the size of the envelope may vary, it is necessary to first locate the address on each envelope before it can be optically read.
Presently, a significant number of the mailpieces utilize either address labels which are attached to the surfaces of the envelopes, or transparent windows through which the addresses are displayed.
In the present invention, signals are generated which represent the positions of the edges of labels and apertures for their use in locating the position of the address information on the mailpiece.
Conventionally, a number of detection systems have been disclosed. For example, in Maxey U.S. Pat. No. 3,890,509 there is disclosed apparatus for detecting the edges of a sawn board by means of light directed at a low angle of incidence to the board, whereby the intensity of sensed light reflected from the board varies as a function of the locations of the board edges. Furthermore, Henderson, in U.S. Pat. No. 4,011,447 discloses a device for detecting the presence of a leading edge and trailing edge of a passing object, and whereby the passing object interrupts a predetermined portion of a light beam and causes a detector/amplifier to signal the presence of the object.
Other detecting devices include U.S. Pat. No. 3,932,755 by Sagawa which pertains to an apparatus for detecting sheets of paper in a pile for paper-feeding purposes whereby when there is only one sheet of paper in the pile, a light beam passes through the single sheet and is reflected at different levels from a high-level reflecting plate and low-level reflecting plate supporting the sheet.
In addition, Nakozawa et al. in U.S. Pat. No. 4,112,309 discloses apparatus for detecting the falls of an IC chip in which a laser beam is directed onto the surface of this moving chip and whereby the light is diffracted at the falls to be detected by photosensing means.